A case of Langerhans cell sarcoma on the scalp: Whole-exome sequencing reveals a role of ultraviolet in the pathogenesis

Left Forearm Langerhans Cell Sarcoma Demonstrated by 18F-FDG PET/CT

ABSTRACT

Langerhans cell sarcoma is a rare neoplastic proliferation of Langerhans cells with a poor prognosis. We report FDG PET/CT findings of Langerhans cell sarcoma in the left forearm of a 77-year-old woman who presented with progressive enlargement of the left forearm mass for over 2 months. 18F-FDG PET/CT demonstrated a high FDG uptake by the mass along with several FDG-avid enlarged lymph nodes in the left arm and axilla. Pathology examination of the biopsied specimen from the left forearm mass led to a diagnosis of Langerhans cell sarcoma.

The Expression of Insulin-Like Growth Factor 2 Messenger RNA-Binding Protein 3 in Langerhans Cell Histiocytosis and Langerhans Cell Sarcoma

Langerhans cell neoplasms, which include Langerhans cell histiocytosis and Langerhans cell sarcoma, are tumors that originate from dendritic cells. Langerhans cell sarcoma is defined as a high-grade neoplasm with overtly malignant cytological features and the Langerhans cell-like phenotype, and generally has a poorer prognosis and more aggressive phenotype than Langerhans cell histiocytosis. Insulin-like growth factor 2 messenger RNA-binding protein 3 (IGF2BP3 or IMP3) is an oncofetal protein that is expressed in various cancer types; its expression is often associated with a poor prognosis and aggressive phenotype. Here, we used immunohistochemistry to evaluate IGF2BP3 expression in Langerhans cell neoplasms. IGF2BP3 expression was scored as negative (< 1%) or positive (≥ 1%) by immunohistochemistry. All 4 patients with Langerhans cell sarcoma (100%) and 6 of 22 pediatric (age < 18 years) patients with Langerhans cell histiocytosis (27.3%) had positive results for IGF2BP3; however, 16 of 22 pediatric patients with Langerhans cell histiocytosis (72.7%) and all 15 adult (age ≥ 18 years) patients with Langerhans cell histiocytosis (100%) had a negative result. Among patients with Langerhans cell histiocytosis, IGF2BP3 expression was independent of sex, location, prognosis, and BRAF V600E staining results. Taken together, these results indicate that IGF2BP3 expression may be a helpful marker for distinguishing Langerhans cell sarcoma from Langerhans cell histiocytosis in adult patients.